Automatic torque wrenching machines are now being used on off-shore drilling platforms to obviate the need for skilled personnel in the highly hazardous area of the rig floor.
Typically, such automatic torque wrenching machines are used to make-up and break out joints in pipes which may be up to 500mm in diameter.
During a make-up operation it is necessary to bring the threaded end (often referred to as the "pin") of one pipe, for example a length of casing, into contact with a threaded socket on the pipe below. The pipes must then be rotated relative to one another until the joint reaches the desired torque.
Because of the substantial weight of the upper pipe it is necessary to support the pipe until the connecting operation is complete to ensure that the weight of the pipe does not damage the threads.
To achieve such jointing it has been proposed to grip the lower pipe with a back-up tong, to grip the upper pipe with a power tong and to provide an advancing mechanism which, as the power tong rotates the upper pipe with respect to the lower pipe lowers the power tong towards the back-up tong.
Whilst this arrangement works tolerably well it has been found necessary to, employ a skilled worker close to the automatic torque wrenching machine to ensure that the thread of the upper pipe initially engages the thread of the socket on the lower pipe correctly. If correct initial engagement does not occur then the advancing mechanism moves the power tong towards the back-up tong prematurely thus damaging the thread.